The present invention generally relates to subsurface safety valves. More particularly, the present invention relates to an apparatus and method to install a replacement safety valve to a location where a previously installed safety valve is desired to be replaced. More particularly still, the present invention relates to communicating with a production zone through a bypass-conduit when a replacement safety valve is closed.
Subsurface safety valves are typically installed in strings of tubing deployed to subterranean wellbores to prevent the escape of fluids from one production zone to another. Absent safety valves, sudden increases in downhole pressure can lead to catastrophic blowouts of production and other fluids into the atmosphere. For this reason, drilling and production regulations throughout the world require safety valves be in place within strings of production tubing before certain operations can be performed.
One popular type of safety valve is known as a flapper valve. Flapper valves typically include a flow interruption device generally in the form of a circular or curved disc that engages a corresponding valve seat to isolate one or more zones in the subsurface well. The flapper disc is preferably constructed such that the flow through the flapper valve seat is as unrestricted as possible. Usually, flapper-type safety valves are located within the production tubing and isolate one or more production zones from the atmosphere or upper portions of the wellbore or production tubing. Optimally, flapper valves function as large clearance check valves, in that they allow substantially unrestricted flow therethrough when opened and completely seal off flow in one direction when closed. Particularly, production tubing safety valves can prevent fluids from production zones from flowing up the production tubing when closed but still allow for the flow of fluids and/or tools into the production zone from above.
Flapper valve disks are often energized with a biasing member (spring, hydraulic cylinder, etc.) such that in a condition with zero flow and with no actuating force applied, the valve remains closed. In this closed position, any build-up of pressure from the production zone below will thrust the flapper disc against the valve seat and act to strengthen any seal therebetween. During use, flapper valves are opened by various methods to allow the free flow and travel of production fluids and tools therethrough. Flapper valves may be kept open through hydraulic, electrical, or mechanical energy during the production process.
Examples of subsurface safety valves can be found in U.S. Provisional Patent Application Ser. No. 60/522,360 filed Sep. 20, 2004 by Jeffrey Bolding entitled “Downhole Safety Apparatus and Method;” U.S. Provisional Patent Application Ser. No. 60/522,498 filed Oct. 7, 2004 by David R. Smith and Jeffrey Bolding entitled “Downhole Safety Valve Apparatus and Method;” U.S. Provisional Patent Application Ser. No. 60/522,499 filed Oct. 7, 2004 by David R. Smith and Jeffrey Bolding entitled “Downhole Safety Valve Interface Apparatus and Method;” all hereby incorporated herein by reference. Furthermore, applicant incorporates by reference U.S. Non-Provisional application Ser. No. 10/708,338 Filed Feb. 25, 2004, titled “Method and Apparatus to Complete a Well Having Tubing Inserted Through a Valve” and U.S. Provisional Application Ser. No. 60/319,972 Filed Feb. 25, 2003 titled “Method and Apparatus to Complete a Well Having Tubing Inserted Through a Valve.”
Over time, a replacement subsurface safety valve may be desired. An existing subsurface safety valve can become stuck or otherwise inoperable either through failure of various safety valve components or because of caked-up hydrocarbon deposits, for example. In these circumstances, sudden increases in production zone pressure can lead to dangerous surface blowouts if the safety valves are not repaired. Because the repair or replacement of a subsurface safety valve formerly required the removal of the string of production tubing from the wellbore, these operations were frequently prohibitively costly for marginal wells. An improved apparatus and method to repair or replace existing subsurface safety valves would be highly desirable to those in the petroleum production industry.